Monolithic ceramic capacitors have often been used under low-frequency low AC voltage or DC low voltage. However, with the advancement of electronics, miniaturization of electronic components is progressing rapidly. This has also accelerated an increase in capacity and miniaturization of monolithic ceramic capacitors. Accordingly, the electric field applied between a pair of opposing electrodes of a ceramic capacitor relatively tends to increase. Under these conditions, there is strong demand for high capacity, low loss, improved insulation performance, and improved reliability.
With this regard, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2000-10366) and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2002-50536) teach a dielectric ceramic composition and a monolithic ceramic capacitor that can withstand the operation under high-frequency high AC voltage or under high DC voltage.
A dielectric ceramic composition set forth in Patent Document 1 contains 100 parts by weight of main component represented by general formula ABO3+aR+bM (wherein ABO3 is a general formula representing a barium titanate solid solution; R represents at least one oxide selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; and M represents at least one oxide selected from the group consisting of Mn, Ni, Mg, Fe, Al, Cr, and Zn), A/B (molar ratio), a, and b satisfying 0.950≦A/B 1.050, 0.12<a≦0.30, and 0.04≦b≦0.30; and 0.8 to 8.0 parts by weight of a sintering aid. This dielectric ceramic composition may further contain X(Zr,Hf)O3 (wherein X is at least one selected from Ba, Sr, and Ca) in an amount of 0.35 mol or less per mole of the barium titanate solid solution and/or D (wherein D is at least one oxide selected from the group consisting of V, Nb, Ta, Mo, W, Y, and Sc) in an amount of 0.02 mol or less per mole of the barium titanate solid solution. The dielectric ceramic composition exhibits a relative dielectric constant of 200 or more, low loss under high frequency and/or high AC voltage, and high specific insulation resistance under high field intensity, satisfies B characteristic and X7R characteristic, and has a long mean time to fail in high-temperature loading test when it is sintered at 1,300° C. or less.
A reduction-resistant dielectric ceramic set forth in Patent Document 2 includes 100 parts by weight of a main component represented by ABO3+aR+bM (wherein ABO3 is a general formula representing a barium titanate solid solution; R represents at least one oxide selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; and M represents at least one oxide selected from the group consisting of Mn, Ni, Mg, Fe, Al, Cr, and Zn), A/B (molar ratio), a, and b satisfying 1.000≦A/B 1.035, 0.005≦a≦0.12, and 0.005≦b≦0.12; and 0.2 to 4.0 parts by weight of a sintering aid. This dielectric ceramic composition may further contain X(Zr,Hf)O3 (wherein X is at least one selected from Ba, Sr, and Ca) in an amount of 0.20 mol or less per mole of the barium titanate solid solution and/or D (wherein D is at least one oxide selected from the group consisting of V, Nb, Ta, Mo, W, Y, Sc, P, Al, and Fe) in an amount of 0.02 mol or less per mole of the barium titanate solid solution. In this dielectric ceramic composition, the crystal axis ratio c/a determined by X-ray diffraction in the temperature range of −25° C. or more satisfies 1.000≦c/a≦1.003 and the local maxima of the relative dielectric constant against temperature change during application of an AC field of 2 Vrms/mm or less at a frequency of 1 kHz is observed at a temperature less than −25° C. The dielectric ceramic composition exhibits low loss and low heat generation under high-frequency and/or high AC voltage and exhibits stable insulating resistance when AC or DC voltage is applied.